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e516451d 1/* $OpenBSD: dh.c,v 1.43 2006/11/06 21:25:28 markus Exp $ */
94ec8c6b 2/*
3 * Copyright (c) 2000 Niels Provos. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "includes.h"
94ec8c6b 27
536c14e8 28#include <sys/param.h>
29
94ec8c6b 30#include <openssl/bn.h>
31#include <openssl/dh.h>
94ec8c6b 32
24436b92 33#include <stdarg.h>
cf851879 34#include <stdio.h>
ffa517a8 35#include <stdlib.h>
00146caa 36#include <string.h>
37
94ec8c6b 38#include "dh.h"
42f11eb2 39#include "pathnames.h"
40#include "log.h"
41#include "misc.h"
94ec8c6b 42
396c147e 43static int
94ec8c6b 44parse_prime(int linenum, char *line, struct dhgroup *dhg)
45{
46 char *cp, *arg;
47 char *strsize, *gen, *prime;
fd06fbe0 48 const char *errstr = NULL;
94ec8c6b 49
50 cp = line;
88299971 51 if ((arg = strdelim(&cp)) == NULL)
52 return 0;
94ec8c6b 53 /* Ignore leading whitespace */
54 if (*arg == '\0')
55 arg = strdelim(&cp);
f11fe301 56 if (!arg || !*arg || *arg == '#')
94ec8c6b 57 return 0;
58
59 /* time */
60 if (cp == NULL || *arg == '\0')
61 goto fail;
62 arg = strsep(&cp, " "); /* type */
63 if (cp == NULL || *arg == '\0')
64 goto fail;
65 arg = strsep(&cp, " "); /* tests */
66 if (cp == NULL || *arg == '\0')
67 goto fail;
68 arg = strsep(&cp, " "); /* tries */
69 if (cp == NULL || *arg == '\0')
70 goto fail;
71 strsize = strsep(&cp, " "); /* size */
72 if (cp == NULL || *strsize == '\0' ||
fd06fbe0 73 (dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
74 errstr)
94ec8c6b 75 goto fail;
db1cd2f3 76 /* The whole group is one bit larger */
77 dhg->size++;
94ec8c6b 78 gen = strsep(&cp, " "); /* gen */
79 if (cp == NULL || *gen == '\0')
80 goto fail;
81 prime = strsep(&cp, " "); /* prime */
82 if (cp != NULL || *prime == '\0')
83 goto fail;
84
b775c6f2 85 if ((dhg->g = BN_new()) == NULL)
86 fatal("parse_prime: BN_new failed");
87 if ((dhg->p = BN_new()) == NULL)
88 fatal("parse_prime: BN_new failed");
ec1f12d3 89 if (BN_hex2bn(&dhg->g, gen) == 0)
c8682232 90 goto failclean;
91
ec1f12d3 92 if (BN_hex2bn(&dhg->p, prime) == 0)
c8682232 93 goto failclean;
94
95 if (BN_num_bits(dhg->p) != dhg->size)
96 goto failclean;
94ec8c6b 97
8b0a55ac 98 if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
99 goto failclean;
100
94ec8c6b 101 return (1);
c8682232 102
103 failclean:
108d362e 104 BN_clear_free(dhg->g);
105 BN_clear_free(dhg->p);
94ec8c6b 106 fail:
54b974dc 107 error("Bad prime description in line %d", linenum);
94ec8c6b 108 return (0);
109}
110
111DH *
db1cd2f3 112choose_dh(int min, int wantbits, int max)
94ec8c6b 113{
114 FILE *f;
cd744742 115 char line[4096];
94ec8c6b 116 int best, bestcount, which;
117 int linenum;
118 struct dhgroup dhg;
119
e2854364 120 if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
121 (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
41e5bd9a 122 logit("WARNING: %s does not exist, using fixed modulus",
123 _PATH_DH_MODULI);
124 return (dh_new_group14());
94ec8c6b 125 }
126
127 linenum = 0;
128 best = bestcount = 0;
129 while (fgets(line, sizeof(line), f)) {
130 linenum++;
131 if (!parse_prime(linenum, line, &dhg))
132 continue;
108d362e 133 BN_clear_free(dhg.g);
134 BN_clear_free(dhg.p);
94ec8c6b 135
db1cd2f3 136 if (dhg.size > max || dhg.size < min)
137 continue;
138
139 if ((dhg.size > wantbits && dhg.size < best) ||
140 (dhg.size > best && best < wantbits)) {
94ec8c6b 141 best = dhg.size;
142 bestcount = 0;
143 }
144 if (dhg.size == best)
145 bestcount++;
146 }
826676b3 147 rewind(f);
94ec8c6b 148
149 if (bestcount == 0) {
826676b3 150 fclose(f);
bbe88b6d 151 logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
0875a0a2 152 return (dh_new_group14());
94ec8c6b 153 }
154
94ec8c6b 155 linenum = 0;
156 which = arc4random() % bestcount;
157 while (fgets(line, sizeof(line), f)) {
158 if (!parse_prime(linenum, line, &dhg))
159 continue;
a7ca6275 160 if ((dhg.size > max || dhg.size < min) ||
161 dhg.size != best ||
162 linenum++ != which) {
108d362e 163 BN_clear_free(dhg.g);
164 BN_clear_free(dhg.p);
94ec8c6b 165 continue;
166 }
167 break;
168 }
169 fclose(f);
a7ca6275 170 if (linenum != which+1)
171 fatal("WARNING: line %d disappeared in %s, giving up",
172 which, _PATH_DH_PRIMES);
94ec8c6b 173
174 return (dh_new_group(dhg.g, dhg.p));
175}
03b8f8be 176
41e5bd9a 177/* diffie-hellman-groupN-sha1 */
03b8f8be 178
179int
180dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
181{
182 int i;
183 int n = BN_num_bits(dh_pub);
184 int bits_set = 0;
397d64d2 185 BIGNUM *tmp;
03b8f8be 186
187 if (dh_pub->neg) {
bbe88b6d 188 logit("invalid public DH value: negativ");
03b8f8be 189 return 0;
190 }
397d64d2 191 if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
192 logit("invalid public DH value: <= 1");
193 return 0;
194 }
195
196 if ((tmp = BN_new()) == NULL)
197 return (-1);
198 if (!BN_sub(tmp, dh->p, BN_value_one()) ||
199 BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
200 BN_clear_free(tmp);
201 logit("invalid public DH value: >= p-1");
202 return 0;
203 }
204 BN_clear_free(tmp);
205
03b8f8be 206 for (i = 0; i <= n; i++)
207 if (BN_is_bit_set(dh_pub, i))
208 bits_set++;
35efb24c 209 debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
03b8f8be 210
211 /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
397d64d2 212 if (bits_set > 1)
03b8f8be 213 return 1;
397d64d2 214
bbe88b6d 215 logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
03b8f8be 216 return 0;
217}
218
219void
220dh_gen_key(DH *dh, int need)
221{
e24bb7d5 222 int i, bits_set, tries = 0;
03b8f8be 223
224 if (dh->p == NULL)
225 fatal("dh_gen_key: dh->p == NULL");
bb92e5cc 226 if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
03b8f8be 227 fatal("dh_gen_key: group too small: %d (2*need %d)",
228 BN_num_bits(dh->p), 2*need);
229 do {
230 if (dh->priv_key != NULL)
108d362e 231 BN_clear_free(dh->priv_key);
b775c6f2 232 if ((dh->priv_key = BN_new()) == NULL)
03b8f8be 233 fatal("dh_gen_key: BN_new failed");
234 /* generate a 2*need bits random private exponent */
83a9aa63 235 if (!BN_rand(dh->priv_key, 2*need, 0, 0))
236 fatal("dh_gen_key: BN_rand failed");
03b8f8be 237 if (DH_generate_key(dh) == 0)
238 fatal("DH_generate_key");
e24bb7d5 239 for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
03b8f8be 240 if (BN_is_bit_set(dh->priv_key, i))
241 bits_set++;
35efb24c 242 debug2("dh_gen_key: priv key bits set: %d/%d",
03b8f8be 243 bits_set, BN_num_bits(dh->priv_key));
244 if (tries++ > 10)
245 fatal("dh_gen_key: too many bad keys: giving up");
246 } while (!dh_pub_is_valid(dh, dh->pub_key));
247}
248
249DH *
250dh_new_group_asc(const char *gen, const char *modulus)
251{
252 DH *dh;
03b8f8be 253
b775c6f2 254 if ((dh = DH_new()) == NULL)
255 fatal("dh_new_group_asc: DH_new");
03b8f8be 256
e516451d 257 if (BN_hex2bn(&dh->p, modulus) == NULL)
03b8f8be 258 fatal("BN_hex2bn p");
e516451d 259 if (BN_hex2bn(&dh->g, gen) == NULL)
03b8f8be 260 fatal("BN_hex2bn g");
261
262 return (dh);
263}
264
265/*
266 * This just returns the group, we still need to generate the exchange
267 * value.
268 */
269
270DH *
271dh_new_group(BIGNUM *gen, BIGNUM *modulus)
272{
273 DH *dh;
274
b775c6f2 275 if ((dh = DH_new()) == NULL)
276 fatal("dh_new_group: DH_new");
03b8f8be 277 dh->p = modulus;
278 dh->g = gen;
279
280 return (dh);
281}
282
283DH *
284dh_new_group1(void)
285{
286 static char *gen = "2", *group1 =
287 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
288 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
289 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
290 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
291 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
292 "FFFFFFFF" "FFFFFFFF";
293
294 return (dh_new_group_asc(gen, group1));
295}
a5c9ffdb 296
41e5bd9a 297DH *
298dh_new_group14(void)
299{
300 static char *gen = "2", *group14 =
301 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
302 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
303 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
304 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
305 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
306 "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
307 "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
308 "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
309 "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
310 "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
311 "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
312
313 return (dh_new_group_asc(gen, group14));
314}
315
a5c9ffdb 316/*
317 * Estimates the group order for a Diffie-Hellman group that has an
318 * attack complexity approximately the same as O(2**bits). Estimate
319 * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
320 */
321
322int
323dh_estimate(int bits)
324{
325
b3c35b71 326 if (bits <= 128)
a5c9ffdb 327 return (1024); /* O(2**86) */
b3c35b71 328 if (bits <= 192)
a5c9ffdb 329 return (2048); /* O(2**116) */
330 return (4096); /* O(2**156) */
331}
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